Optical media, as typically used today, includes a variety of supplementary information that is in addition to the data recorded in the optical media. The supplementary information is frequently presented in elaborate form, consistent with the marketing, advertising or other goals of the manufacturer. The supplementary information may be included in various fashions, such as through the use of stick on labels, inks or through other techniques.
Labeling or markings are typically applied to the “non-read” side of a optical disc, such as a Compact Disc (CD) or a Digital Versatile Disc (DVD), for indicating information such as the source of the disc and a listing of the information recorded thereon. The placement of markings on the non-readout side of optical media permits the use of a variety of marking technologies, ranging from simple to complex. Placement of markings on the read-side of optical media, particularly in the area where data is recorded, is a greater challenge, as the markings can interfere with the use of the optical media.
Considering that approximately 1 billion DVDs and more than 4 billion CDs are produced annually (as estimated by the International Recording Media Association), the potential advertising space has been equated to 1 billion magazine advertising pages, 300 million newspaper advertising pages, or 3 million billboards. Accordingly, the value of incorporating markings into optical media, especially the currently unmarked readout side, is very high.
One example of a technique for marking an optical media is disclosed in the International Patent Application Publication No.: WO 99/65696, entitled “Permanent Image Formation,” and published on 23 Dec. 1999. The application discloses a method and apparatus for forming a permanent image on a substrate including CD, DVD and packaging (particularly those formed from recycled polycarbonate and/or recycled PET). The application discloses that the printing process therein differs from the prior art in that ink is applied to a substantial portion of a substrate surface, instead of only in the image areas. One skilled in the art will recognize that, in the case of optical media, the ink is limited to providing for images on the non-readout area of the optical media. For example, since pigments used in the ink typically include particles, the ink would likely cause scatter of a readout light (laser), thus inhibiting readout of the data features. Further, the disclosed use of an infrared (IR) laser to impart the image implies the ink would interfere with a normal data readout process since CD and DVD media use near-IR lasers in the readout mechanism.
Prior attempts to place markings on the read side have been made. Reference may be had to U.S. Patents directed towards optical storage systems. For example, U.S. Pat. No. 5,549,953, entitled “Optical Recording Media Having Optically-Variable Security Properties” by Li Li, issued Aug. 27, 1996, discloses a technique to prevent counterfeiting of various substrates through introducing thin film structures having optically variable security properties and encoded optical data. Another U.S. Pat. No. 5,510,160, entitled “Optical Storage Media Having Visible Logos”, by Sullivan, et al., issued on Apr. 23, 1996. This patent also discloses a technique to prevent counterfeiting of optical storage media, specifically through producing a visible logo on the read side of the substrate. Although these patents provide for incorporation of markings that may have certain advantages, any advantages are limited. That is, for example, the markings are visible only under certain conditions, and complicated or expensive manufacturing processes are called for to produce finished product. Furthermore, the degree of control, or complexity of the marking may be less than desired for effective advertising or other information bearing schemes.
Other examples involving a coating applied to an optical media can be found in U.S. Pat. No. 6,051,298 “Optical Disc Having Protective Films.” This patent discloses an optical disc having a protective film, the film having good transmissivity and high hardness against abrasion, and in U.S. Pat. No. 6,322,868 B1 “Use and Manufacturing Applications of Polymer/Dye-Based Thin Layer Coatings for Enhancement of the Quality of Recording On and Readout From the Optical Storage Media,” which discloses use of a thin layer coating for the improvement of the quality of the encoded digital information. Another example includes U.S. Pat. No. 6,338,933 “Methods and Apparatus for Rendering an Optically Encoded Medium Unreadable.” This patent discloses including optically activated materials to degrade the reflectivity of a surface.
However, the foregoing patents have not taken advantage of certain advances in materials. For example, reference may be had to International Patent Publication No.: WO 02/101462 A1 “Laser Marking Method” published on 19 Dec. 2002, applied for by Ciba Specialty Chemicals Holding Inc. This publication discloses a method of coloring a polymeric material containing a latent acid, a color former, and optionally further ingredients by irradiation with UV-light. Another International Patent Publication No.: WO 02/100914 A2, applied for by Ciba Specialty Chemicals Holding Inc., is entitled “Polymeric Material, Containing a Latent Acid.” This publication discloses a polymeric material containing a latent acid which can be converted to an acid by irradiation by a laser and optionally further ingredients. Another example is disclosed in U.S. Pat. No. 5,028,792 “System for the Visualization of Exposure to Ultraviolet Radiation,” issued Jul. 2, 1991 to Mullis. This patent discloses photochemical systems for the direct visualization of exposure to ultraviolet radiation, in which a photoacid is formed upon irradiation with ultraviolet light and causes a dye to undergo a visible color change.
Further patents disclose compounds and techniques for applying colorforming materials as a coating. Consider, for example, U.S. Pat. No. 6,013,601, “Laser Printing Method and Substrate” issued Jan. 11, 2000; and the Continuation thereof, U.S. Pat. No. 6,140,267, issued Oct. 31, 2000. These patents disclose a method and a substrate for printing information wherein at least one coating is applied to a substrate, the coating containing photosensitive colorforming components. When heated with a laser beam, a chromic change occurs in the at least one coating thereby providing for the printing of information.
Patents disclosing colorforming coatings include U.S. Pat. No. 4,552,830, entitled “Carbonylic Halides as Activators for Phototropic Compositions”, issued Nov. 12, 1985 to Reardon et al. and U.S. Pat. No. 4,343,885, entitled “Phototropic Photosensitive Compositions Containing Fluoran Colorformer”, issued Aug. 10, 1982 to Reardon. Both patents disclose compositions useful for the production of photoresist films for the electronics industry. These compositions are disclosed as containing a polymerizable, crosslinkable or curable component with a photoinitiator, a colorformer, and an activator; where the composition becomes insoluble and change color under the influence of actinic radiation.
It is known to apply radiation sensitive coatings to objects for the visualization of exposure to radiation. Refer to U.S. Pat. No. 5,436,115, entitled “Systems for the Visualization of Exposure to Ultraviolet Radiation,” issued Jul. 25, 1995. Likewise, invisible fluorescent images may be developed using similar technology and acid sensitive fluorescent dyes, such as those reported in “Positive and Negative Fluorescent Imaging Induced by Naphthalimide Polymers” by He Tian, Jiaan Gan, Kongchang Chen, Jun He, Qun Liang Songb and XiaoYuan Houb, Journal of Materials Chemistry 2002, 12, 1262-1267.
One further example is disclosed in U.S. Pat. No. 5,885,746 “Photosensitive Resin Composition, Photosensitive Printing Plate Using the Same and Method of Manufacturing Printing Master Plate,” issued Mar. 23, 1999 to Iwai, et al. This patent discloses a photosensitive resin composition comprising a high polymer binder, a monomer, a photopolymerization initiator generating a radical on exposure to visible light, and an optically activated acid generating agent, generating an acid on exposure to wavelengths of 200 nm to 380 nm, with a color former developing color in the presence of an acid. Among other things, this patent discloses use of dispersing agents, which indicate inhomogeneity, a property that would cause laser scatter in an optical media readout system. Also, the initiators disclosed in this patent are sensitive to visible light and require the use of an oxygen barrier layer to affect adequate curing. Use of an oxygen barrier layer is a substantial hindrance to the application of these materials to quantities of optical disc, as manufacturing environments do not typically provide for a dark and/or oxygen free environment. Further such additional steps present economic and production burdens that would serve to limit use of the marking system.
Non-limiting examples of existing embodiments of optical media (prior art) are provided in FIGS. 1-8. In FIG. 1, a prior art optical media 8 is depicted as a compact disc (CD). The CD 8 includes a substrate 17 (typically formed of polycarbonate), a metallized layer 14 (also referred to as a reflecting layer 14), and a protective layer 12. A label is disposed on a label side 7, over the protective layer 12, which is typically formed of a UV curable acrylic. A readout light (as depicted by the upward pointed arrow) penetrates the readout side 2 to provide a readout signal for interpreting data features known as-pits 5 and lands 6. Aspects of other embodiments of optical media 8 are presented in FIGS. 2-8.
Other formats of optical media 8 are presented in order to illustrate variations in architecture. FIG. 2 depicts an optical media 8 as a single sided/single layer embodiment of a Digital Versatile Disc (DVD). In general, DVD 8 includes substrate layers 17, reflective layers 14, and a bonding layer 15. The structure shown in FIG. 2 correlates to aspects of optical media 8 commonly referred to as “DVD-5.” FIG. 3 depicts another embodiment of a prior art optical media 8, where a single sided/dual layer embodiment of a DVD is shown. In this embodiment, the reflective layer 14 includes a semi-reflective layer 14-1 and a substantially reflective layer 14-2. The substrate layer 17 includes a first substrate layer 17-1, and a second substrate layer 17-2. This structure correlates to aspects of optical media 8 commonly referred to as “DVD-9.” In this embodiment, two layers of data features are provided on the one side of the DVD 8. Other examples of prior art optical media 8 include a dual sided/single layer DVD, as shown in FIG. 4. This structure correlates to aspects of optical media 8 commonly referred to as “DVD-10.” A dual sided/dual layer embodiment of a DVD 8 is shown in FIG. 5. This structure correlates to aspects of optical media 8 commonly referred to as “DVD-18.” This embodiment of a DVD includes two sides, each with a dual layer format. Both layers of each side are manufactured on a single polycarbonate substrate layer 17, and subsequently bonded together at the bonding layer 15. DVD-18 has the largest capacity of the family but is the most difficult and complex to manufacture. A unique stamper is needed to create each of the four substrate layers 17. DVD-14 is a related format in which only one half of the disc 8 is a dual layer disc 8. This format contains approximately 14 gigabytes of data. DVD-14 is slightly easier to manufacture than a DVD-18, since one side is a DVD-5. Further examples of optical media 8 include a hybrid SACD, as shown in FIG. 6; a hybrid DVD, as shown in FIG. 7; and, a DVD Plus, as shown in FIG. 8.
Combination disc formats, for example combining DVD-ROM on one side with DVD-RAM on the other, are known. Such discs 8 are double sided discs and are read from both sides. Hybrid SACD is a format developed by Philips and Sony and combines a SACD (i.e., physically a DVD layer) with a CD layer. Both layers are read from the same side, which means that the SACD layer must be reflective for a red laser but will transmit an infra red CD laser. Such discs can be played on both a CD player (which will read the CD layer) and a SACD player.
Hybrid DVD is a similar format to the hybrid SACD with a conventional DVD data layer over a CD data layer. DVD Plus refers to a disc comprising a CD bonded to a DVD substrate. The resulting disc allows both DVD and CD data to be read from one disc, like a hybrid DVD, but the disc is read from both sides. Neither format is commonly available as yet.
Each format of optical media 8 is described by certain specifications. For example, for the CD shown in FIG. 1, the specification thickness for the substrate layer 17 is 1.2 mm, while the pits 5 are separated by about 125 nm from the lands 6. In DVD, as shown in FIGS. 2-5, the substrate layers 17 are typically 0.6 mm thick.
This cursory examination of these popular (but few) embodiments of optical media 8 serves to point out that a variety of layers exist within the various formats for optical media 8. These layers each contain a certain amount of material selected for providing certain properties, such as clarity and rigidity. One skilled in the art can surmise that the various layers may be constructed of an assortment of materials, while providing for the functionality of the optical media 8.
The assortment of materials is typically limited by such criteria as for light transmission at a given wavelength, viscosity during application, and other optical properties. Understandably, materials are frequently in development to improve the performance of optical media 8.
Examples of recently developed disc-molding materials include PLEXIGLAS VOD-100 produced by Elf Atochem of North America Inc., Philadelphia, Pa. which is a grade of acrylic thermoplastic specially designed for optical disc manufacturing; a similar material is ACRYLITE DQ501 from CYRO Industries, Rockaway, N.J.; another product is Polycyclohexylethylene (PCHE), from Dow Plastics, Midland, Mich., which is a saturated cyclic hydrocarbon that is derived from styrene monomer, and said to have exceptional optical purity and clarity, with a refractive index of 1.51 and high light transmittance across the full spectrum, including the blue-green range. Further non-limiting examples of disc-molding materials are LEXAN products from General Electric of Pittsfield, Mass., which include models OQ1040L, OQ1050 and OQ1030L.
The wide use of optical media 8 call for advanced marking schemes. This need is growing rapidly with changes in optical media technology and growing demand. For example, the advent of dual sided optical media 8 necessitates the development of a marking scheme that does not interfere, or substantially interfere, with a readout laser.
Such a scheme should provide enhanced marking, identification, authentication and encoding capabilities for optical media. The scheme should provide for rapid production of images, text, or other optically encoded information on the label and/or read side of the optical media. Furthermore, the scheme should further provide for markings that are robust and durable in environments where optical media may be used.